Please make sure to mention both the title and author, and how the book relates to simple living for you!
I like “Goodbye, Things” by Fumio Sasaki. It’s a book about minimalism. I don’t personally live like a minimalist to the same extent he does, but it gave me a lot of things to consider in terms of what I actually need to live the life I want. As it turns out, it’s surprisingly little.
The Underachiever’s Manifesto is a good little book on the topic, as well as of course The Abide Guide.
I really liked Everyday Adventures from Lonely Planet. It’s about simple, and some cheap, activities you can do in the area you live. Or you can do them while traveling. I found it quite inspiring and it gave me ideas about what I can do where I live and not to only be adventurous when I’m out traveling.
The Early Buddhist Texts, which explain the very frugal, minimal lifestyles of Buddhist monks. They have few possessions, and share communal facilities - which is what monasteries are.
I’m a big fan of Marie Kondo’s books. Reading them just makes me want to live simpler.
The Little Book of Ikigai by Ken Mogi is another. Gets me thinking about doing what’s important, not doing everything.